lib: quoteIfNeeded should not escape the backslashes in unicode code points.

hledger-lib/Hledger/Utils/String.hs

@@ -118,13 +118,17 @@ underline s = s' ++ replicate (length s) '-' ++ "\n"
 -- | Double-quote this string if it contains whitespace, single quotes
 -- or double-quotes, escaping the quotes as needed.
 quoteIfNeeded :: String -> String
-quoteIfNeeded s | any (`elem` s) (quotechars++whitespacechars++redirectchars) = show s
+quoteIfNeeded s | any (`elem` s) (quotechars++whitespacechars++redirectchars) = showChar '"' $ escapeQuotes s "\""
                 | otherwise = s
+  where
+    escapeQuotes []       x = x
+    escapeQuotes ('"':cs) x = showString "\\\"" $ escapeQuotes cs x
+    escapeQuotes (c:cs)   x = showChar c        $ escapeQuotes cs x
 
 -- | Single-quote this string if it contains whitespace or double-quotes.
 -- No good for strings containing single quotes.
 singleQuoteIfNeeded :: String -> String
-singleQuoteIfNeeded s | any (`elem` s) whitespacechars = "'"++s++"'"
+singleQuoteIfNeeded s | any (`elem` s) (quotechars++whitespacechars) = "'"++s++"'"
                       | otherwise = s
 
 quotechars, whitespacechars, redirectchars :: [Char]

tests/i18n/unicode-account-matching.test

@@ -6,3 +6,12 @@ hledger -f - register τράπ
 >>>
 2009-01-01 проверка             τράπεζα                     10 руб        10 руб
 >>>=0
+
+hledger -f - balance -N " ét"
+<<<
+2020-09-19 Test
+    assets:a ét            5
+    assets:b
+>>>
+                   5  assets:a ét
+>>>=0